Systems and methods for changing coolant in a linear accelerator

ABSTRACT

Systems and methods for replacing coolant of an x-ray tube assembly having a closed cooling system include a service port that is operatively connected to a portion of the x-ray tube assembly and a vacuum assisted service kit that is operatively coupled to the service port. Used coolant is drained from the x-ray tube assembly, and thereafter a vacuum is drawn on the x-ray tube assembly via the service kit. Replacement coolant within a vacuum tank of the service kit is degassed under a vacuum. The degassed replacement coolant is provided into the cooling system from the vacuum tank, preferably by pushing under pressure with an inert gas to prevent the introduction of any air into the replacement coolant. The replacement coolant may be pressurized in the cooling system with the inert gas. Thereafter, the service kit may be disconnected from the service port.

RELATED APPLICATION DATA

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/827,834, filed Mar. 14, 2013, which is hereby incorporatedby reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to a system and method for changingcoolant in an x-ray tube system.

BACKGROUND

Linear accelerators can be used for radiation treatment in the medicalfield and can include targeting systems using x-ray machines, forexample. Linear accelerators have a limited life span and are expensive.For example, an x-ray tube in a linear accelerator may have a warrantyusage of some predetermined number of uses. Thereafter, the owner of themachine usually needs to either replace the x-ray tube or service thex-ray tube to extend the useful lifespan of the machine. Frequently, thecost to service the machine is significantly less than the cost ofreplacing an x-ray tube or an entire linear accelerator. Therefore, itis desirable to have systems and methods of servicing and maintaining alinear accelerator that be used as an alternative to replacing a linearaccelerator.

FIG. 1 is a diagrammatic illustration of an exemplary radiationgenerating machine 10. The machine 10 includes a base support 12, amoveable gantry 14, and a linear accelerator 16 carried within thegantry 14. The linear accelerator 16 includes an x-ray tube 18, whichmay be carried in an arm of the gantry 14, and a cooling system 20 forcooling the x-ray tube 18 during use. The cooling system 20 includes aheat exchanger 22, coolant circulation conduits 24 that connect the heatexchanger 22 to the x-ray tube 18, and usually additional equipment,such as pumps, valves, and/or switches to control the flow andcirculation of coolant between the heat exchanger 22 and the x-ray tube18.

The x-ray tube 18 generates significant amounts of heat during its use.The generated heat, however, can damage the working parts of the x-raytube 18. Therefore, the cooling system 20 is used to cool the x-ray tube18 and thereby prevent premature failure of the working parts of thex-ray tube 18.

The cooling system 20 operates by circulating a coolant, usually oil,such as Shell Diala AX, through the x-ray tube 18 and to the heatexchanger 22. The heat exchanger 22 cools the coolant and then thecoolant is returned to the x-ray tube 18 through the circulationconduits 24, where the cooling process is repeated. However, the coolantbreaks down over time due to the heat generated by the x-ray tube, whichdiminishes the ability of the coolant to function at its optimalperformance levels. When this happens, either the entire x-ray tube 18must be replaced or the old coolant can be replaced with new coolant.

As indicated above, it is generally significantly less expensive toreplace the coolant rather than buying an entirely new x-ray tube 18.However, there are some limitations that must be met. One significantlimitation is that the coolant should not have any air entrappedtherein. Entrapped air in the coolant can degrade the coolant in thex-ray tube 18. Therefore, in replacing the coolant, it is important tominimize or eliminate any entrained air in the coolant. To this end, thecooling system 20 of the linear accelerator 16 is a closed system, whichis sealed to prevent air from entering into the cooling system and thecoolant.

SUMMARY

According to some aspects of the present disclosure, systems and methodsare disclosed that allow coolant from a linear accelerator to bereplaced under vacuum to ensure that air and other unwanted gasses areremoved from the replacement coolant and from the cooling system whenthe replacement coolant is placed into the cooling system.

In some exemplary arrangements, a coolant replacement system for alinear accelerator includes a service port operatively connected to aportion of the linear accelerator, a vacuum tank operatively connectedto the service port to supply replacement coolant to a cooling system ofthe linear accelerator, a vacuum pump operatively connected to thevacuum tank, and an inert gas supply operatively connected to the vacuumtank. The inert gas supply is preferably operatively connected to thevacuum tank by way of a bladder, wherein the bladder is operativelyconnected to the vacuum tank, and the inert gas supply is operativelyconnected to the bladder. One or more flow control valves arranged toallow the vacuum pump to draw a vacuum in the vacuum tank and coolantconduit of the cooling system to degass the coolant conduit andreplacement coolant in the vacuum tank. One or more flow control valvesarranged to allow the inert gas supply to push degassed coolant into theevacuated coolant conduit.

In other exemplary arrangements, a method of replacing coolant in aclosed cooling system of a linear accelerator is disclosed. The coolingsystem is opened, and used coolant is removed from the opened coolingsystem. Thereafter, a service port is operatively connected to thecooling system and a vacuum tank is operatively connected to the serviceport. Air is evacuated from the cooling system by drawing a vacuum inthe cooling system. Replacement coolant in the vacuum tank is degassedby drawing a vacuum in the vacuum tank. The degassed replacement coolantis pushed from the vacuum tank into the evacuated cooling system with aninert gas. Thereafter, the cooling system is closed with the degassedreplacement cooling coolant disposed in the cooling system withoutallowing air to enter into the cooling system.

In yet other exemplary arrangements, a service kit for replacing usedcoolant in a cooling system of a linear accelerator having a serviceport installed to allow vacuum access to the cooling system isdisclosed. The service kit includes a vacuum tank, a recouplable vacuumconnector for operatively coupling and decoupling the vacuum tank withthe service port, a vacuum pump operatively coupled to the vacuum tank,a bladder operatively coupled to the vacuum tank, a supply of inert gasoperatively coupled to the bladder, and a plurality of flow controlvalves arranged to selectively isolate the vacuum tank from any one ormore of the supply of inert gas, the vacuum pump, and the service port.The vacuum pump is arranged to draw a vacuum from the vacuum tank.

In further accordance with any one or more of the foregoing aspects andexemplary arrangements, a coolant replacement system, a method, aservice kit, and/or components thereof according to the teachings of thepresent disclosure optionally may include any one or more of thefollowing optional forms.

In some optional forms, the service port includes a vacuum couplingoperatively coupled to the coolant conduit and a shutoff valveoperatively disposed between the vacuum coupling and the coolant conduitto open and/or close a flow of fluid between the vacuum coupling and thecoolant conduit.

In some optional forms, the service port includes a tube coupling and avacuum coupling, the tube coupling adapted to be coupled to an exteriorsurface of the closed x-ray tube system adjacent a drain opening of theclosed x-ray tube system, and the vacuum coupling operatively coupled tothe tube coupling, the closed x-ray tube system comprising a sight glassremovably disposable within the drain opening to open and close a flowof fluid between the vacuum coupling and coolant conduit of the coolingsystem. In one optional form, the service port further includes asealing element disposed within the tube coupling and surrounding thedrain opening of the closed x-ray tube system.

In some optional forms, the vacuum tank includes a tank with an openingand a resealable lid removably covering the opening. The vacuum tank mayinclude an exhaust port operatively connecting the vacuum pump to thevacuum tank, a feed port operatively connecting the vacuum tank to thebladder, and/or a dip tube operatively connecting the vacuum tank to theservice port. The dip tube may have an inlet dispose below the exhaustport and the feed port.

In some optional forms, one or more valves are operatively arranged toselectively isolate various components of the system. A first flowcontrol valve may be operatively disposed between the feed port and thebladder. A second flow control valve may be operatively disposed betweenthe exhaust port and the vacuum pump. A third flow control valve mayoperatively disposed between the inlet of the dip tube and vacuumconnector. A fourth flow control valve may be operatively disposedbetween the third flow control valve and the vacuum connector. One ormore of the valves may be shutoff valve or a check valve

In some optional forms, the vacuum connector includes a quick disconnectplug and a quick disconnect coupler arranged to selective couple anddecouple with each other in a manner arranged to maintain a vacuumpresent in the conduits.

In some optional forms, the bladder may include one or more of aflexible walled container, a bellows, and an expansion tank.

In some optional forms, the inert gas supply includes a tank containinginert gas. A sixth flow control valve may be operatively disposedbetween the bladder and the tank. A pressure regulator may beoperatively disposed between the bladder and the tank. The inert gas maybe, for example, nitrogen.

In some optional forms, the cooling system is closed after removing theused coolant.

In some optional forms, the service port is operatively connected to acoolant conduit of the cooling system.

In some optional forms, the service port is operatively connected to anexterior surface (e.g., on the end) of an x-ray tube of the x-ray tubesystem adjacent a drain opening of the x-ray tube.

In some optional forms, a sight glass covering the drain opening of thex-ray tube is removed to open the cooling system. The cooling system canbe closed by (i) pushing the sight glass toward the drain openingthrough a vacuum coupling disposed between the vacuum tank and thecooling system and at least partially filled with replacement coolant,and (ii) re-inserting the sight glass into the drain opening.

In some optional forms, the evacuated cooling system is operativelyisolated from the vacuum tank before degassing the replacement coolant,for example by closing a flow control valve. The evacuated coolingsystem may be operatively reconnected in a vacuum sealed manner to thevacuum tank before pushing the degassed replacement coolant from thevacuum tank into the evacuated cooling system, for example, by openingthe flow control valve.

In some optional forms, a vacuum is drawn from the air bladderoperatively connected to the vacuum tank to contract the bladder,preferably while degassing the replacement coolant.

In some optional forms, the replacement coolant is pushed into thecooling system by providing inert gas to the vacuum tank through thebladder through, preferably while the bladder is contracted. A positivepressure may be provided to the inert gas sufficient to re-expand thebladder after the degassed replacement fluid is pushed into theevacuated cooling system, for example, by expanding the bladder toapproximately 25 percent capacity.

In some optional forms, a fifth flow control valve is operativelydisposed between the bladder and the supply of inert gas and arranged toselectively isolate the bladder from the supply of inert gas.

In some optional forms, the coupling is in the form of a t-couplinghaving a first branch connected to a first portion of the circulationconduit, a second branch connected to a second portion of thecirculation conduit, and a third branch connected to a connectionconduit extending to the recouplable vacuum connector. The flow controlvalve of the service port may be a shutoff valve disposed along theconnection conduit.

Other viable aspects and optional forms of the system, method, and kitdisclosed herein will be apparent upon consideration of the followingdetailed description and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevational view of a radiation generatingmachine including a linear accelerator according to the prior art;

FIG. 2 is a schematic illustration of an x-ray tube system and a coolantreplacement system including a service port and a service kit accordingto the teachings of the present disclosure;

FIG. 3 is a partial isometric view of an x-ray tube showing a site glassdisposed in a drain opening; and

FIG. 4 is a partial isometric view of the x-ray tube similar to FIG. 3but with a nozzle disposed in the drain opening.

FIG. 5 is a schematic illustration of another x-ray tube system andanother coolant replacement system including a service port and aservice kit according to the teachings of the present disclosure.

FIG. 6 is a partial isometric view of one end of the x-ray tube of FIG.5 with a sight glass installed.

FIG. 7 is an exploded view of the components of the service port of FIG.5.

FIG. 8 is an isometric view depicting the service port of FIG. 5 coupledto the end of the x-ray tube.

FIG. 9 is another isometric view depicting the service port of FIG. 5coupled to the end of the x-ray tube.

FIG. 10 is a cross-sectional view, taken along line 10-10 in FIG. 9,depicting the service port coupled to the end of the x-ray tube.

FIG. 11 is an isometric view depicting the service kit of FIG. 5operatively connected to the service port with a service kit coupling.

DETAILED DESCRIPTION

Turning now to the drawings, FIG. 2 illustrates a coolant replacementsystem 28 for an x-ray tube system 30 and a service kit 32 for replacingthe coolant in the x-ray tube system 30 according to a first technicalexample of the present disclosure. The x-ray tube system 30 includes anx-ray tube 18 and a cooling system 20, including a heat exchanger 22 andcoolant circulation conduits 24. In addition, the x-ray tube system 30is provided with a service port 34, which is preferably permanentlyinstalled along one of the coolant circulation conduits 24, for example,between the heat exchanger 22 and the x-ray tube 18. The service kit 32may be coupled and decoupled to the service port 34 to allow a vacuum tobe drawn from the coolant circulation conduits 24, and thereby from thecooling system 20 and the x-ray tube 18, through the service kit 32, andto allow replacement coolant, such as oil, to be transferred into thecoolant circulation conduits 24 from the service kit 32 without allowingany substantial amount of air to enter into the coolant circulationconduits 24. In this arrangement, the coolant replacement system 28provides an effective way to replace used coolant in the x-ray tubesystem 30 with replacement or new coolant in a way that more reliablyensures that the replacement coolant and the entire coolant circulationsystem of the x-ray tube system 30 is free of unwanted air.

The service port 34 is preferably permanently installed on the x-raytube system 30 to provide fluid access to the coolant circulationconduits 24 for drawing a vacuum from the cooling system 20 and thex-ray tube 18 and providing new replacement coolant into the circulationconduits. The service port 34 includes a coupling 36 that is operativelydisposed along the cooling system 20 to maintain a vacuum therein. Thecoupling 36 may be a T-coupling disposed along one of the coolantcirculation conduits 24 and sealed to maintain a vacuum or any othercoupling capable of providing similar fluid access into and out of thecoolant circulation conduits. The service port 34 further includes arecouplable vacuum connector 38 operatively connected to the coupling36, such as with or along a stub conduit 40, and a service flow controlvalve 42, such as a shut off valve, operatively disposed along the stubconduit 40 between the vacuum coupling 36 and the recouplable vacuumconnector 38. The flow control valve 42 can be selectively opened and/orclosed so as to selectively isolate the recouplable vacuum connector 38from the coupling 36 to either provide fluid access into and out of thecoolant circulation conduits 24 and/or to close the cooling system 20.

The service kit 32 can include, at least in part, a vacuum tank 44, avacuum pump 46, a supply of inert gas 48, and another recouplable vacuumconnector 50 for operatively coupling and decoupling with therecouplable vacuum connector 38 of the service port 34. The vacuum pump46 is operatively connected to the vacuum tank 44, for example, with aconduit 51 connected to an exhaust port 52 of the vacuum tank 44, suchthat the vacuum pump 46 can evacuate air and thereby draw a vacuum inthe vacuum tank 44. The supply of inert gas 48 is carried within a tank54 that is operatively connected to a feed port 56 of the vacuum tank 44by one or more conduits 58 a and 58 b. A bladder 60 is operativelydisposed along the conduits 58 a and 58 b to provide a collapsible andexpandable container or diaphragm operatively disposed between thesupply of inert gas 48 and the vacuum tank 44. A conduit 62 operativelyconnects the recouplable vacuum connector 50 to the vacuum tank 44 so asto provide fluid communication between the recouplable vacuum connector50 and the interior of the vacuum tank 44.

The vacuum tank 44 includes a container body 44 a defining an interiorarea and a top opening into the interior, and a lid 44 b for sealinglyclosing the top opening. One or more locks 44 c, such as nuts, wingnuts, clamps, or other known locking devices, are used to releasablyseal and lock the lid 44 b onto the container body 44 a covering theopening. A dip tube 64 extends into the interior of the vacuum tank 44and has an inlet 66 disposed near the bottom of the interior of thecontainer body 44 a. The dip tube 64 is carried, for example, by the lid44 b and operatively connects to the conduit 62. Each of the exhaustport 52 and the feed port 56 is disposed near a top portion of thevacuum tank 44, such as along the top of the container body 44 a nearthe open top, such that, when the vacuum tank is 44 is in an uprightposition, the inlet 66 of the dip tube 64 is disposed at or near alowest point of the vacuum tank 44 and the exhaust port 52 and the feedport 56 are disposed above the inlet 66. In this manner, replacementcoolant 68 disposed in the interior of the vacuum tank 44 covers theinlet 66 of the dip tube 64 and has a top surface disposed below theexhaust port 52 and feed port 56, as will be described in more detailbelow.

In addition to the foregoing, the service kit 32 can also include anumber of flow control valves that are operatively arranged to allowvarious components of the service kit 32 and the service port 34 to beselectively operatively connected and isolated, i.e., placed in fluidconnection or isolation, from other components and to control flow offluid through the coolant replacement system 28. For example, a firstflow control valve 70 is operatively disposed along the conduit 58 abetween the feed port 56 and the bladder 60 to allow the vacuum tank 44to be selectively isolated from the bladder 60. The first flow controlvalve 70 may be, for example, an on/off valve, such as a globe valve, adisc valve, a butterfly valve, or other type of on/off valve. A secondflow control valve 72 is operatively disposed between the vacuum tank 44and the vacuum pump 46, such as along the conduit 51, to allow thevacuum tank 44 to be selectively isolated from the vacuum pump 46. Thesecond flow control valve 72 may be an on/off valve or a one way checkvalve. A third flow control valve 74 is operatively disposed between therecouplable vacuum connector 50 and the vacuum tank 44 along the conduit62. And, a fourth flow control valve 76 is operatively disposed betweenthe third flow control valve 74 and the recouplable vacuum connector 50along the conduit 62. Each of the third and fourth flow control valves74 and 76 is operable to isolate the recouplable vacuum connector 50from the vacuum tank 44, and may be on/off valves. A fifth flow controlvalve 78 is operatively disposed between the bladder 60 and the tank 54along the conduit 58 b to allow the inert gas supply 48 to beselectively isolated from the bladder 60 and the vacuum tank 44. Thefifth flow control valve 78 may be an on/off valve, such as a globevalve or butterfly valve or other type of valve that may be selectivelyturned on and/or off to allow for stop fluid flow therethrough. Each ofthe first through fifth flow control valves 70, 72, 74, 76, and 78 isoperable independently of the other flow control valves. A pressureregulator 80 can be connected to the tank 54 to regulate the pressure ofinert gas flowing from the tank 54 to the bladder 60 and the vacuum tank44, preferably at a pre-selected or selectable pressure, in a mannerwell understood in the art.

The recouplable vacuum connectors 38 and 50 together form a vacuumconnector 82 between the service port 34 and the service kit 32 that canbe coupled and decoupled in a manner to preserve a vacuum and/orpositive pressure within the vacuum tank 44 and/or the coolantcirculation conduits 24 of the cooling system 20 of the x-ray tubesystem 30. Many vacuum connectors are known and would be suitable foruse as the vacuum connector 82. In one example, the recouplable vacuumconnector 38 may be a quick disconnect plug and the recouplable vacuumconnector 50 may be a complimentary quick disconnect coupler known inthe art. While the service port 34 has not been expressly described asbeing part of the service kit 32, in other versions, the service kit 32can include the service port 34 as well.

The vacuum pump 46 may be any type of pump suitable for drawing a vacuumfrom the vacuum tank 44 preferably, the vacuum pump is sufficient todraw a vacuum, for example, 20, 30, 40, or more inches of mercury.However, the vacuum pump 46 may be sized and selected in any mannernecessary and sufficient to draw a desired vacuum from the vacuum tank44 and from the coolant circulation conduits 24 as explained inadditional detail hereinafter.

The bladder 60 may take any of various forms of a container that is bothcollapsible and then re-expandable. For example, the bladder 60 mayinclude a bellows, a flexible walled plastic jug or bag, a hard-walledcontainer with one or more moveable walls that allow the container toeffectively expand and/or collapse, or any of other various known orsimilar expandable and contractible containers. In some versions, thebladder 60 can include what is conventionally referred to as a “let-upkit,” for example.

Each of the conduits 24, 40, 62, 51, 58 a, and 58 b, may be made of anysuitable material and be in the form of for example rubber hoses,braided hoses, multi-walled hoses, metal hoses, metal tubes, or anyother conduit suitable for transporting fluids in a closed pressurizedsystem.

With the service kit 32 and related components configured as described,a detailed exemplary technical method of using the cooling replacementsystem 28 to replace the coolant in the cooling system 20 of the x-raytube system 30 is described with reference to FIG. 2. Before changingthe coolant in the x-ray tube system 30, it is of course preferable tostop operation the x-ray tube system 30, including turning off the x-raytube 18 and turning off any circulation pumps and/or other components ofthe radiation generating device 10.

Next, used coolant is removed from the x-ray tube 18 and the coolingsystem 20. This can be accomplished in situ, that is, with the x-raytube system 30 remaining in its operative position in the housing of itssupport structure, such as the gantry 14, or by removing the x-ray tubesystem 30, either partially or completely, from its support structure.With reference to FIGS. 3 and 4, one preferred way to remove the coolantis to remove, e.g., unscrew, a sight glass 90 from a drain opening 96located on the x-ray tube 18 to open or unseal the coolant circulationsystem of the x-ray tube system 30. Thereafter, a nozzle 92 as shown inFIG. 4 is fitted into, e.g., screwed into, the drain opening 96. Thenozzle 92 is arranged to allow the coolant to be poured out of the x-raytube 18 without dripping onto the exterior of the x-ray tube 18.Thereby, the used coolant can be drained from the cooling system 20 in away that keeps the x-ray tube 18 clean. The nozzle 92 has an end flange92 a defining an annular recess 92 b surrounding the opening 92 c of thenozzle 92. The nozzle 92 includes a male connector (not shown) at anopposite end from the end of flange 92 a with external threads forthreaded connection to the drain opening 96. With the nozzle 92 attachedto the drain opening 96, the used coolant may be removed from the x-raytube system 30 either in situ, as carried in the gantry 14, or the x-raytube system 30 may be completely removed from the gantry 14 for theremoval and replacement of the coolant. If the coolant is replaced insitu, a hose, for example, may be connected to the end flange 92 a tocarry the used coolant to a receptacle without getting used coolant allover the support structure, such as the gantry 14.

After the coolant has been drained from the x-ray tube 18, the nozzle 92is removed from the drain opening 96 and the sight glass 90 isre-installed to seal the drain opening 96.

After the cooling system 20 has been drained and resealed, the serviceport 34 is installed. Of course, if the service port 34 is alreadyinstalled, the following installation steps may be skipped at thispoint. To install the service port 34, one of the coolant circulationconduits 24 is severed, and a first portion of the conduit 24 isconnected to a first branch of the coupling 36, which in this case is at-coupling, and a second portion of the conduit 24 is connected to asecond branch of the t-coupling. The stub conduit 40 is attached to thethird branch of the t-coupling, and the valve 42 and recouplable vacuumconnector 38 are either already installed or are thereafter installedoperatively connected to the t-coupling 36.

Next, the service kit 32 is operatively coupled to the service port 34by connecting the recouplable vacuum connector 50 to the recouplablevacuum connector 38. In this manner the vacuum tank 44 is operativelyconnected with the cooling system 20 via the service port 34 to allowfluid to be transferred under pressure and/or vacuum between the coolantcirculation conduits 24 and the interior of the vacuum tank 44.

The vacuum pump 46 is operatively coupled to the vacuum tank 44 at theexhaust port 52.

Next, the cooling system 20 is evacuated by drawing a vacuum through thevacuum tank 44 and the service port 34 with the vacuum pump 46. To dothis, the service flow control valve 42 and the second, third, andfourth flow control valves 72, 74, 76 are opened. The first flow controlvalve 70 at this point is preferably closed. The vacuum pump 46 isturned on and draws a vacuum on the vacuum tank 44 and the coolingsystem 20, preferably up to approximately thirty inches of mercury,although other vacuum pressures may also or alternatively be useddepending on various parameters of the various components. In somecases, it is estimated that the vacuum pump 46 may need to be activatedfor approximately fifteen minutes to ensure that a sufficient vacuum hasbeen drawn in the coolant circulation conduits 24, the heat exchanger22, and the x-ray tube 18. Of course, this depends upon the size andperformance capabilities of the vacuum pump 46.

Next, the cooling system 20 is isolated from the vacuum tank 44, forexample, by closing the service flow control valve 42 in the serviceport 34.

After the evacuated cooling system 20 has been isolated from the vacuumtank 44, an amount of coolant sufficient to fill the cooling system 20as appropriate is added into the vacuum tank 44. This may beaccomplished, for example, by unlocking the locks 44 c, opening the lid44 b, pouring replacement coolant 68 into the interior of the containerbody 44 a, and then resealing the lid 44 b onto the tank 44 with thelocks 44 c.

Next, if the bladder and inert gas supply 48 have not already beenconnected to the vacuum tank 44, with the flow control valve 70 closed,the bladder 60 is operatively connected to the vacuum tank 44 byattaching the conduit 58 a to the bladder 60. The bladder 60 is alsooperatively connected to the inert gas supply 48 by connecting theconduit 58 b to the tank 54. In this manner the inert gas supply 48 isoperatively connected to the vacuum tank 44 via the bladder 60.

With the third flow control valve 74 closed, thereby isolating thevacuum tank 44 from the vacuum connector 82, the vacuum pump 46 isactivated with the second flow control valve 72 opened to draw a vacuum,preferably of approximately thirty inches of mercury, inside the vacuumtank 44. A vacuum is also drawn from the bladder 60, thereby collapsingthe bladder 60. The vacuum may be held for any necessary period of timeto ensure that all air is removed from the replacement coolant 68 thatresides in the tank 44. In this way, the replacement coolant 68 isdegassed and all air is substantially eliminated from the replacementcoolant 68.

With the vacuum pump 46 still drawing a vacuum from the vacuum tank 44,the third flow control valve 74 (and the fourth and service flow controlvalves 76 and 42, respectively, if necessary) is opened, therebyoperatively reconnecting the vacuum tank 44 to the coolant circulationconduits 24. The vacuum pump 46 remains running to ensure that a desiredand balanced vacuum pressure, e.g., approximately thirty inches ofmercury, is drawn across both the vacuum tank 44 and the cooling system20 of the x-ray tube system 30. The amount of time that this takesvaries of course upon the operating characteristics of the vacuum pump46. After the desired vacuum pressure is attained across the vacuum tank44 and the coolant circulation conduits 24, the second flow controlvalve 72 is closed and the vacuum pump 46 may be shut off. Thus at thispoint the vacuum tank 44, the conduits 62 and 40, and the coolantcirculation conduits 24 and other portions of the cooling system 20 ofthe x-ray tube system 30 are under a single vacuum pressure in asubstantially sealed or closed system.

Next, the bladder 60 is filled with inert gas, such as nitrogen, fromthe inert gas supply 48. To do this, the first flow control valve 70 isclosed after the vacuum has been drawn on the bladder 60. Then, thefifth flow control valve 78 is opened, and pressurized gas inside thetank 54 transfers into the bladder 60 until a predefined pressure set bythe regulator 80 is achieved. This expands the bladder 60. The flowcontrol valve 78 is subsequently closed after the bladder 60 has beenfilled with the inert gas.

Next, the replacement coolant 68 that resides in the tank 44 underpressure is forced from the tank 44 into the evacuated cooling system 20with the inert gas. To do this, the first flow control valve 70 isopened, preferably slowly so as to minimize any sudden pressure surges.Atmospheric pressure on the bladder 60 pushes the inert gas into theupper portion of the vacuum tank 44 via the feed port 56 and therebyforces the replacement coolant 68 up into the inlet 66 of the dip tube64 and from there into the coolant circulation conduits 24, which werepreviously under a vacuum, via the conduits 62 and 40. After thepressure in the vacuum tank 44 and the remaining portions of the coolingsystem 20 reach atmospheric pressure due to compression of the bladder60, the fifth flow control valve 78 may be slowly opened to allow inertgas from the tank 54 under positive pressure to provide additionalpositive pressure into the vacuum tank 44 and thus also the coolingsystem 20 of the x-ray tube system 30, thereby pressurizing thereplacement coolant 68 in the coolant circulation conduits 24. Althoughthe replacement coolant 68 may be positively pressurized to any desiredpressure, in one preferred method, the inert gas supply 48 is leftoperatively connected to the vacuum tank 44 by having the first andfifth flow control valves 70 and 78 opened until the bladder 60 expandsto approximately a 25% full or expanded condition. After the replacementcoolant 68 has been pushed into the coolant circulation conduits 24 bythe inert gas and achieved the desired pressure, the service flowcontrol valve 42 and the third and fourth flow control valves 74 and 76are closed, and thereafter the first flow control valve 70, andoptionally the fifth flow control valve 78 are also closed. In thiscondition, the service port 34 and thus the cooling system 20 of thex-ray tube system 30 is isolated from the vacuum tank 44 andpressurized, and preferably the vacuum tank 44 is also isolated from theinert gas supply 48.

At this point, it is preferable to verify that there is no air in thecooling system 20. This may be accomplished, for example, by rotatingthe gantry 14 or the x-ray tube 18 and visually observing whether anyair bubbles are visible in the sight glass 90 of the x-ray tube 18.Other suitable methods of checking for the presence of air in thecooling system 20 are also equally acceptable.

Next, if no air has been identified in the cooling system 20, the flowcontrol valve 42 is closed, and the service kit 32 may be disconnectedfrom the service port 34 by uncoupling the recouplable vacuum connector50 from the recouplable vacuum connector 38. If air bubbles areidentified through the sight glass 90, the sight glass 90 can beslightly loosened such that the pressurized bubbles naturally expel toatmosphere.

FIG. 5 illustrates a coolant replacement system 128 for an x-ray tubesystem 130 and the service kit 32 used to replace the coolant in thex-ray tube system 130 in accordance with a second technical example ofthe present disclosure. The coolant replacement system 128, like thecoolant replacement system 28, provides an effective way to replace usedcoolant in the x-ray tube system 130 with replacement or new coolant ina way that more reliably ensures that the replacement coolant and theentire coolant circulation system of the x-ray tube system 130 is freeof unwanted air.

The x-ray tube system 130 is similar to the x-ray tube system 30described above, with common components indicated by common referencenumerals and any differences outlined below. The x-ray tube system 130generally includes an x-ray tube 118 and the cooling system 20, which,as noted above, includes the heat exchanger 22 and the coolantcirculation conduits 24. Unlike the x-ray tube system 30, wherein theservice port 34 is coupled along one of the conduits 24, the x-ray tubesystem 130 includes a service port 134 that is removably coupled to aportion of the x-ray tube 118, as will be described in greater detailbelow. However, like the x-ray tube system 30, the service port 134,when coupled to the x-ray tube 118, provides fluid access to the coolantcirculation conduits 24 for drawing a vacuum from the cooling system 20and the x-ray tube 118 and providing new or replacement coolant into thecirculation conduits 24.

The x-ray tube 118 is substantially similar to the x-ray tube 18described above. As illustrated in FIG. 6, the x-ray tube 118 has an end180, a neck 182, and a drain 186 coupled to and partially disposedwithin the neck 182. The neck 182 extends outward from the end 180 andis defined by a cylindrical wall 188 and an annular opening 189 (seeFIG. 10) defined by the wall 188. A first part of the drain 186 isdisposed within the annular opening of the neck 184, while a second partof the drain 186 has a diameter that is larger than an inner diameter ofthe cylindrical wall 188 and thus rests on the cylindrical wall 188. Assuch, the drain 186 is raised relative to the neck 182. The x-ray tube118 further includes a drain opening 196 formed within the drain 186. Asight glass 190 is removably disposable within the drain opening 196 toopen and close the drain 186, and, thus, unseal or seal the coolingsystem 20. When the sight glass 190 is disposed within the drain opening196, as is illustrated in FIG. 6, the sight glass 190 seals the drainopening 186, and, in turn, the cooling system 20.

FIG. 7 illustrates the components of the service port 134 in greaterdetail. The service port 134 in this version includes a tube coupling200, a seal 204, a ring 208, and a vacuum coupling 212. Unlike theservice port 34, which includes a service flow control valve, such asthe flow control valve 42, that can be selectively opened or closed soas to isolate the service port 34 from the service kit 32, the serviceport 134 does not include any type of service flow control.

The tube coupling 200 is preferably made of metal and has an annularshape defined by a cylindrical wall 216 surrounding and defining acentral opening 220. The cylindrical wall 216 has internal threads 224for threaded connection with the vacuum coupling 212. The centralopening 220 is sized to receive or accommodate the seal 204, the ring208, and a portion of the vacuum coupling 212. The seal 204 in thisversion is an o-ring sized to be disposed or seated between the neck 182of the x-ray tube 118 and the coupling 212. The ring 208 in this versionis preferably a metal ferrule that has an outer diameter that is largerthan an outer diameter of the seal 204. The ring 208 is sized to bedisposed or seated between the neck 182 of the x-ray tube 118 and thecoupling 212 proximate or adjacent to the seal 204. The vacuum coupling212 has a body 226, a flange 228 disposed at and extending outward fromone end 230A of the body 226, and external threads 232 formed proximateto an opposite end 230B of the body 226. The external threads 232 areconfigured for threaded connection with the internal threads 224 of thetube coupling 200. The vacuum coupling 212 further includes an opening236 defined by and extending through the body 226.

It will be appreciated that service port 134 can vary from the serviceport 134 illustrated in FIG. 7. More specifically, the service port 134can include additional, different, or fewer components than the tubecoupling 200, the seal 204, the ring 208, and the vacuum coupling 212.The tube coupling 200 can vary in shape (e.g., can be rectangular,triangular, or have some other shape in cross-section), size, and/orconstruction. For example, the tube coupling 200 can have externalthreads instead of the internal threads 224. The seal 204 can vary inshape, size, and/or take the form of a different type of sealingelement. Likewise, the ring 208 can vary in shape (e.g., can berectangular, triangular, or have some other shape in cross-section). Thecoupling 212 can also vary in shape, size, and/or construction. In otherexamples, one or more of the components of the service port 134 can beintegrally formed with one another or coupled to one another in adifferent manner.

FIGS. 8-10 illustrate one example of how the service port 134 can becoupled to (e.g. installed on) the x-ray tube 118. In this example, theservice port 134 is coupled to the x-ray tube 118 via four clamps 250coupled (e.g., secured) to the end 180 of the x-ray tube 118. Asillustrated in FIGS. 8 and 9, a bottom end 231 of the tube coupling 200is seated on and flush with the end 180 of the x-ray tube 118 and aroundthe neck 182 such that the cylindrical wall 216 of the tube coupling 200circumscribes and extends upward from the neck 182 and the drain 186 ofthe x-ray tube 118. The tube coupling 200 is retained in this positionby the clamps 250. Each clamp 250 has a base portion 252 coupled (e.g.,fastened) to the end 180 of the x-ray tube 118 and an arm portion 254that extends inward from the base portion 252 and partially extends overand interferingly contacts a top end 258 of the cylindrical wall 216 ofthe tube coupling 200. Each clamp 250 is secured in this position by aplurality of fasteners 260 disposed in an opening formed in the baseportion 252 and an opening formed in the end 180 of the x-ray tube 118.As best illustrated in FIG. 10, the seal 204 and the ring 208 aredisposed inside the tube coupling 200 and seated on an end face 181 ofthe x-ray tube 118 adjacent the raised portion of the drain 186. Thevacuum coupling 212 is threaded into the tube coupling 200 via thethreads 224, 232. Threading the vacuum coupling 212 down into the tubecoupling 200, in the direction of the arrow in FIG. 10, causes thebottom end 230B of the vacuum coupling 212 to compress the ring 208 andseal 204 tightly against the end face 181 of the x-ray tube 118, therebycreating a fluid tight seal. In the version illustrated in FIG. 7, thering 208 or the seal 204 can make sealing contact with the end face 181while the other makes contact with the bottom end 230B of the vacuumcoupling 212. Regardless, the interaction between the ring 208 and theseal 204 helps prevent the seal 204 from being overcompressed and/orotherwise destroyed under compression. Of course, in other versions, thering 208 may be eliminated, or the configuration of the ring 208 and theseal 204 can be replaced with other sealing mechanisms. In the describedmanner, the service port 134, particularly the couplings 200, 212, aresealed to the x-ray tube 118 maintain a vacuum. So constructed andpositioned, the service port 134 provides fluid access into and out ofthe cooling system 20, particularly the coolant circulation conduits 24of the cooling system 20.

It will be appreciated that the service port 134 need not be coupled tothe x-ray tube 118 in the exact manner described above. In someexamples, the above-described steps of coupling the service port 134 tothe x-ray tube 118 can occur in a different order. While the clamps 250are described as being installed in the proper position before thevacuum coupling 212 is threaded to the tube coupling 200, the clamps 250can alternatively be installed in the proper position after thecouplings 200, 212, the seal 204, and the ring 208 are coupled to oneanother or at some other point in time.

As illustrated in FIG. 11, the coolant replacement system 128 furtherincludes a service kit coupling 300 that operatively connects theservice kit 32 described above with the service port 134 for the purposeof replacing the coolant in the x-ray tube system 130. In this version,the coupling 300 is a T-coupling 304 that three arms—arms 308, 312, and316—and three ports (not shown) defined by those arms 308, 312, and 316,respectively. The first arm 308 is disposed within a portion of theservice port 134. More specifically, the first arm 308 is disposedwithin the opening 236 of the vacuum coupling 212, with the first portdisposed within the opening 236 and operatively connected to the drainopening 186. The first arm 308 is frictionally retained in position bythe body 226 of the coupling 212. The second arm 312, particularly thesecond port, is sized to receive a vacuum gauge 320, which can, whenconnected, display the pressure within the service kit coupling 300(which should correspond to the desired vacuum or positive pressure).Although not explicitly illustrated herein, the third arm 316 isconfigured to be operatively coupled to the service kit 32, particularlythe recouplable vacuum connector 50, thereby facilitating an operativeconnection between the service kit 32 and the service port 134. As alsoillustrated in FIG. 10, a plurality of fittings (in this case, three)can be used to sealingly connect the various components together. Theplurality of fittings may, for example, be or include KF-25 fittings,KF-40 fittings, other suitable components, or combinations thereof.

In other examples, the service kit 32 can be operatively connected tothe service port 134 in a different manner. For example, the recouplablevacuum connector 50 can be directly connected to one or more componentsof the service port 134, thereby obviating the need for the service kitcoupling 300.

When desired, the cooling replacement system 128 can be used to replacethe coolant in the cooling system 20 of the x-ray tube system 130. Asnoted above, before changing the coolant in the x-ray tube system 130,it is preferable to stop operation of the x-ray tube system 130,including turning off the x-ray tube 118 and turning off any circulationpumps and/or other components of the radiation generating device 10.

At this point, used coolant can be removed from the x-ray tube 118 andthe cooling system 20. This can be accomplished in the same mannerdescribed above (i.e., removing the sight glass 190 from the drainopening 196 and using the nozzle 92 to drain the used coolant) or can beaccomplished in a different manner. For example, the sight glass 190 canbe removed from the drain opening 196 and the used coolant can bedrained through the service port 134 using the service kit 32 or someother component(s). After the coolant has been drained from the x-raytube 118, the sight glass 190 can, but need not, be re-installed to sealthe drain opening 196. Alternatively, the sight glass 190 need not bere-installed until after the coolant has been replaced.

After the cooling system 20 has been drained, the service port 134 isinstalled. Alternatively, of course, the service port 134 may already beinstalled (e.g., before the cooling system 20 is drained). In eithercase, the service port 134 is installed in the manner described above.Next, the service kit 32 is operatively coupled to the service port 134by connecting the recouplable vacuum connector 50 to the T-coupling 304.In this manner, the vacuum tank 44 is operatively connected with thecooling system 20 via the service port 134 to allow fluid to betransferred under pressure and/or vacuum between the coolant circulationconduits 24 and the interior of the vacuum tank 44. The process fordoing so is identical to the process described above in connection withthe service port 34.

After the coolant has been replaced, the sight glass 190 is re-installedto seal the drain opening 196. To ensure that no air is in or gets intothe cooling system 20, the vacuum gauge 320 can be removed and the sightglass 190 can be inserted into the coupling 300 (via the port defined bythe second arm 312), pushed toward the drain opening 196 through thecoupling 300 and the vacuum coupling 212 (via, e.g., a tool), which atthis point is at least partially filed with the replacement coolant, andre-inserted into the drain opening 196. Alternatively, the sight glass190 can be re-installed in a different manner (e.g., with the serviceport 134 removed), in which case any number of suitable methods can beused to check for the presence of air in the cooling system 20.

After the sight glass 190 has been re-installed, the service kit 32 canbe disconnected from the service port 134. The service port 134 can alsobe disconnected at this time, can be disconnected at another time, orneed not be disconnected at all. Alternatively, the service kit 32 canbe disconnected at a different time (e.g., before the sight glass 190has been re-installed.

Based on the foregoing, it should be appreciated that the systems andmethods of replacing coolant in a closed cooling system of an x-ray tubesystem and various components thereof according the teachings of thepresent disclosure are useful for doing so in a manner that ensures thatthe replacement coolant will be free of any unwanted air. The systemsand methods described herein also provide a cost effective alternativeto currently known methods of replacing a coolant in an x-ray tubesystem and/or simply replacing the x-ray tube system when its maximumusage capacity has been reached due to degradation of the used coolant.

1. A coolant replacement system, comprising a service port adapted to beoperatively connected to a closed x-ray tube system; a vacuum tankoperatively connected to the service port to supply replacement coolantto a cooling system of the closed x-ray tube system; a vacuum pumpoperatively connected to the vacuum tank to selectively draw a vacuum onthe vacuum tank; an inert gas supply operatively connected to the vacuumtank; one or more flow control valves disposed between the vacuum pumpand the vacuum tank and arranged to allow the vacuum pump to beselectively isolated from or fluidly connected to the vacuum tank,whereby the vacuum pump can draw a vacuum on the vacuum tank and thecooling system; and one or more flow control valves disposed between theinert gas supply and the vacuum tank and arranged to allow the inert gassupply to be selectively isolated from or fluidly connected to thevacuum tank, whereby the inert gas supply can push coolant from thevacuum tank and into the evacuated cooling system.
 2. The coolantreplacement system of claim 1, wherein the service port is adapted to beoperatively connected to a coolant conduit of the cooling system andcomprises: a vacuum coupling operatively coupled to the coolant conduit;and a shutoff valve operatively disposed between the vacuum coupling andthe coolant conduit to open and close a flow of fluid between the vacuumcoupling and the coolant conduit.
 3. The coolant replacement system ofclaim 1, wherein the service port comprises: a tube coupling adapted tobe coupled to an exterior surface of the closed x-ray tube systemadjacent a drain opening of the closed x-ray tube system; and a vacuumcoupling operatively coupled to the tube coupling, the closed x-ray tubesystem comprising a sight glass removably disposable within the drainopening to open and close a flow of fluid between the vacuum couplingand a coolant conduit of the cooling system.
 4. The coolant replacementsystem of claim 3, wherein the service port further comprises a sealingelement disposed within the tube coupling and surrounding the drainopening of the closed x-ray tube system.
 5. The coolant replacementsystem of claim 1, wherein the vacuum tank comprises: a tank with anopening; and a resealable lid removably covering the opening.
 6. Thecoolant replacement system of claim 1, further comprising: a bladderoperatively connected between the vacuum tank and the inert gas supply.7. The coolant replacement system of claim 4, wherein the vacuum tankfurther comprises: an exhaust port operatively connecting the vacuumpump to the vacuum tank; a feed port operatively connecting the vacuumtank to the bladder; and a dip tube operatively connecting an interiorof the vacuum tank to the service port, the dip tube having an inletdisposed below the exhaust port and the feed port.
 8. The coolantreplacement system of claim 7, further comprising: a first flow controlvalve operatively disposed between the feed port and the bladder; asecond flow control valve operatively disposed between the exhaust portand the vacuum pump; a third flow control valve operatively disposedbetween the inlet of the dip tube and a vacuum connector; and a fourthflow control valve operatively disposed between the third flow controlvalve and the vacuum connector.
 9. The coolant replacement system ofclaim 4, wherein the inert gas supply comprises: a tank containing aninert gas; a fifth flow control valve operatively disposed between thebladder and the tank; and a pressure regulator operatively disposedbetween the bladder and the tank.
 10. The coolant replacement system ofclaim 1, further comprising a vacuum connector disposed between theservice port and the vacuum tank, the vacuum connector comprising aquick disconnect plug and a quick disconnect coupler.
 11. A method ofreplacing a coolant in a closed cooling system of an x-ray tube system,the method comprising: opening the cooling system; removing used coolantfrom the opened cooling system; operatively connecting a service port tothe cooling system; connecting a vacuum tank to the service port;evacuating air from the cooling system by drawing a vacuum on the vacuumtank and the cooling system through the service port; at least partiallyfilling the vacuum tank with a quantity of replacement coolant; drawinga vacuum on the replacement coolant in the vacuum tank; pushing thereplacement coolant out from the vacuum tank, through the service port,and into the evacuated cooling system with an inert gas; and closing thecooling system after the replacement coolant is pushed therein whilesubstantially preventing air from entering the cooling system.
 12. Themethod of claim 11, further comprising closing the cooling system afterremoving the used coolant.
 13. The method of claim 11, whereinoperatively connecting the service port to the cooling system comprisescoupling the service port to a coolant conduit of the cooling system.14. The method of claim 11, wherein operatively connecting the serviceport comprises coupling the service port to an exterior surface of anx-ray tube of the x-ray tube system adjacent a drain opening of thex-ray tube, the service port being in fluid communication with thecooling system.
 15. The method of claim 11, wherein opening the coolingsystem comprises removing a sight glass covering a drain opening of thex-ray tube of the x-ray tube system, and wherein closing the coolingsystem comprises: pushing the sight glass toward the drain openingthrough a vacuum coupling disposed between the vacuum tank and thecooling system and at least partially filled with the replacementcoolant; and re-inserting the sight glass into the drain opening. 16.The method of claim 11, further comprising: operatively isolating thecooling system from the vacuum tank before drawing a vacuum on thereplacement coolant; operatively reconnecting the cooling system to thevacuum tank before pushing the replacement coolant out from the vacuumtank, through the service port, and into the evacuated cooling system.17. The method of claim 16, wherein operatively isolating the coolingsystem from the vacuum tank comprises closing at least one flow controlvalve disposed between the cooling system from the vacuum tank.
 18. Themethod of claim 16, wherein operatively reconnecting the cooling systemto the vacuum tank comprises opening the at least one flow controlvalve.
 19. The method of claim 11, wherein drawing a vacuum on thereplacement coolant further comprises drawing a vacuum on an air bladderoperatively connected to the vacuum tank, thereby contracting the airbladder.
 20. The method of claim 11, wherein drawing a vacuum on thereplacement coolant comprises degassing the replacement coolant.
 21. Themethod of claim 19, further comprising filling the air bladder at leastpartly with the inert gas after drawing the vacuum on the replacementcoolant.
 22. The method of claim 21, wherein pushing the replacementcoolant out from the vacuum tank comprises providing the inert gas tothe vacuum tank through the bladder.
 23. A service kit for replacingused coolant in a cooling system of an x-ray tube system having aservice port, the service kit comprising: a vacuum tank; a firstrecouplable vacuum connector for operatively coupling and decoupling thevacuum tank with the service port; a vacuum pump adapted to be operablycoupled to the vacuum tank and arranged to draw a vacuum on the vacuumtank; a collapsible bladder adapted to be operatively coupled to thevacuum tank; a supply of inert gas adapted to be operatively coupled tothe bladder; a first flow control valve adapted to be coupled betweenthe supply of inert gas and the vacuum tank and arranged to selectivelyisolate the supply of inert gas from the vacuum tank; a second flowcontrol valve adapted to be coupled between the vacuum pump and thevacuum tank and arranged to selectively isolate the vacuum pump from thevacuum tank; and a third flow control valve adapted to be coupledbetween the service port and the vacuum tank and arranged to selectivelyisolate the vacuum tank from the service port.
 24. The service kit ofclaim 23, wherein the first flow control valve is operatively disposedbetween the bladder and the vacuum tank.
 25. The service kit of claim23, further comprising: a fifth flow control valve adapted to beoperatively disposed between the bladder and the supply of inert gas andarranged to selectively isolate the bladder from the supply of inertgas.